Opportunistic Feedback in Collaborative Spectrum Sensing for Cognitive Radio

Collaborative sensing in cognitive radio networks is able to significantly improve the detection probability for the existence of primary user transmission. However, it is usually assumed that there exists orthogonal channels for the cognitive users to send the detection information to the decision center, which is not realistic. In this paper, we consider a practical scenario in which there is a random access channel shared by different cognitive radio users. We then propose a two-threshold opportunistic feedback scheme to judiciously select some cognitive users who have much confidence in the spectrum sensing decision to share the random access channel. The thresholds are determined to maximize the detection probability while keeping the collision of the random access as minimal. The analytical results of the distributed spectrum sensing with the proposed opportunistic feedback are derived. Numerical results show that the proposed opportunistic feedback scheme in distributive spectrum sensing is superior to the conventional cooperative spectrum sensing where the orthogonal access channels are applied.